(1) Field of the Invention
This invention relates to a substrate container for containing semiconductor wafers, glass substrate for photomasks, glass substrates for liquid crystal displays, substrates for optical disks, and so on (hereinafter simply called “substrates”), and a load port apparatus and a substrate treating apparatus applicable to the substrate container.
(2) Description of the Related Art
Conventionally, there exists a substrate container which supports substrates in two modes (as disclosed in Japanese Unexamined Patent Publication No. 2007-227941, for example). This substrate container includes a housing, a lid, racks and cushions. The housing accommodates a plurality of substrates. The lid is attachable to and detachable from to the housing. The racks and cushions are arranged in the housing. The racks support the substrates in a state of lower surfaces of the substrates contacting the racks. The cushions hold the substrates in a state of the substrates being spaced from the racks and being stationary. Thus, the substrate container can support the substrates in a mode in which the racks support the substrates and a mode in which the cushions support the substrates.
When the lid is detached from the housing, the racks support the substrates. Consequently, an external transport mechanism provided outside the substrate container can unload the substrates from the substrate container and load the substrates into the substrate container. When the lid is attached to the housing, the cushions support the substrates. Consequently, the substrates can be protected conveniently when the substrate container is transported. Thus, the mode in which the racks support the substrates and the mode in which the cushions support the substrates are switched between each other by attachment and detachment of the lid to/from the housing.
However, Inventors herein have found out that the conventional example with such construction has the following drawbacks.
That is, even when the lid has separated from the housing, the cushions can remain holding the substrates and the substrates would not disengage from the cushions. Conceivable causes of this include scars formed on surfaces of the cushions, and abrasion powder resulting from abrasion between the cushions and substrates and having deposited on the cushions.
When the lid has separated from the substrate container and the substrates would not disengage from the cushions, the substrates cannot be placed properly on the racks and intervals between the substrates cannot be secured properly. It is therefore difficult for the external transport mechanism to advance into clearances between the substrates and unload the substrates from the substrate container. Also when the lid has separated from the substrate container and the substrates would not disengage from the cushions, movement of the substrates will remain restricted by the cushions. For example, the substrates become caught by the cushions to be unable to move easily. Consequently, it becomes difficult for the external transport mechanism to hold the substrates and unload the substrates from the substrate container.